Signaling system



Feb.6,1934. M; B. LONG "1,945,557

' SIGNALING SYSTEM Fild Oct. 1. 1925 2 Shee ts-Sheet 1 W e/#01:- Mm/nkg15. 100;

by auM [#19 Feb. 6, 1934. M. B. LONG SIGNALING SYSTEM Filed Oct. 1'.1926 2 Sheets-Sheet 2 m; F b. 6, 1934 v 1,945,557

UNITED STATES PATENT OFFICE SIGNALING SYSTEM Maurice 13. Long, GlenRidge, N. 1., alsignor to Western Electric Company, Incorporated, NewYork, N. Y., a corporation of New York Application October 1, 1928.Serial No. 138,854

9 Claims. (Cl. 250-40) This invention relates to control of electriccirmay be prepared for this instantaneous tuning to cuits or apparatus.whatever wave lengths the local stations Just An object of the inventionis to control elecmentioned may have, these tuning capacities, tricalconditions or characteristics of electric cirwhich for convenience maybe termed instanta- 6 cuits or apparatus, as for example, easily andneous tuning capacities are adjustable. The stao quickly to vary thefrequency selectivity of a sigtion selecting keys may be looking keys,the opnal receiving circuit. I eration of each causing the release ofthe key last A further object is to enable the desired control operated.The receiver, without sufiering disoi' the electrical conditions orcharacteristics of turbance of its adjustment for the instantaneous 10the circuits or apparatus tobe effected-from a tuning just mentioned,may be tuned to any one 35 distance. of a range of wave lengths,includingthe wave It is also an object of the-invention to facililengthsof the several local stations mentioned tate reception of signals, asfor example radio above, by means of an additional variable consignals,and operation ofa sound reproducing denser, this condenser beingconnected in the device, as for example a phonograph, alternatuningcircuit by operation of an additional lock- 7 tively. ing key. Uponoperation of this key the station Another object is to facilitate theassociation selecting key last operated is released, and disof soundreproducing apparatus, or amplifying connects its tuning capacity fromthe tuning cirand reproducing apparatus, with either a mecuit. Operationof any station selecting key when chanically operated electrical pick-updevice or the above mentioned additional variable con- 7 anelectrically. operated pick-up device. denser is in circuit releases theabove mentioned It has been suggested that, where a radio sysadditionalkey, thus causing the additional varitem is linked with a wire system,for tuning a able condenser to be withdrawn from the tuning radiotransmitting circuit from a distance, relays circuit.

, be provided to control a variable inductance in According to anotheraspect of the invention a go the antenna circuit and control theconnection selector switch may be used to control the conanddisconnection of variable condensers in the nection of the instantaneoustuning elements. If circuit which feeds the antenna circuit, and fordesired, the tuning of the radio receiver may be tuning a radioreceiving circuit from a distance, controlled from a point distant fromthe in- -relays control the connection and disconnection stantaneoustuning capacities, as for example by 5 of variable condensers in thecircuit fed by the having selecting means at a telephone receiverreceiving antenna. The relays in each case may which is operated by theradio receiver and is at a be controlled by rotary switches and'otherrelays. distance from the instantaneous tuning capacities which areoperated over wires when a call is and havingthe selector control theswitching of originated from a subscriber's station. the tuningcapacities in and out of circuit.

As examples of applications of the present in- Craft Patent No.1,559,679, November 3, 1925, vention there are disclosed herein severalsimple discloses a system in which a common loud radio receiving systemsembodying specific forms speaker, together with its amplifier, may beconof the invention. -In accordance with this innected to the output ofa radio receiving circuit 40 vention, condensers in the receivingantenna cironto an electric phonograph, as desired. The 95 cuit andcondensers in the circuit fed from the switching operation isaccomplished by means of antenna circuit are adjusted at the receiver ora three position switch so that it is possible to at a distancetherefrom, for tuning the receiver. have the loud speaker connected tothe radio ap- The adjustment may be effected by a series of paratus orto the phonograph, or entirely diskeys or a series of keys and relays,or by rotary connected. mo

selector switches. In a specific embodiment of the instant inven- Inaccordance with the invention, in order to tion, there is an electricalpick-up device adapted substantially instantaneously tune a radio retobe mechanically operated by a phonograph ceiver to select wave lengthsof, say, a few first record and an electrical pick-up device, such as aclass local radio broadcasting stations, station radio receiver, bothofwhich are adapted to be 105 selecting keys or switches may be operated,the separately associated with a common amplifying operation of eachswitch causing a diflerent preelement and a loud speaker by means whichare determined value of tuning capacity to be insert automaticallycontrolled by the phonograph ed substantiallyinstantaneously, in thetuning operating mechanism to bring about the altercircuit of thereceiver. In order that the receiver native connection and disconnectionof the two no with the amplifying apparatus. It will be understood thatthe amplifier may be dispensed with where sufiicient volume ofreproduction is obtainable without it. 1

Other objects and features of the invention will be apparent from thefollowing description and claims:

' Fig. 1 of the drawings is a diagram of a radio receiving systemembodying one form of the invention; Fig. 2 is a diagram of a radioreceiving system embodying another form of the invention; and Fig. 3 isa diagram of a radio receiving system embodying still another form ofthe invention.

In Fig. 1 there is an antenna circuit, comprising an antenna 5, aninductance 6, and three optional or alternative paths to ground frominductance 6. Relays 7 and 8 controlled by keys or' push buttons 9, 10,11 and 12, are adapted to connect any one of the three paths in theantenna circuit. Of these paths, one includes a variable condenser 15and a coil 18, a second includes a variable con-.- denser 16 and a coil19, and the third includes a variable condenser 17 and a coil 20. Thesethree coils constitute the primary windings of a coupling coil 21, thesecondary winding 22 of which forms part of the tuned input circuit of aradio receiver. This input circuit may be tuned by any one of threecondensers 15, 16 and 17 optionally or alternatively .connected incircuit by the relays 7 and 8 under control of the keys 9, 10, 11 and12. Theradio receiver comprises an electric space discharge detectortube 24 feeding an electric space discharge amplifier tube 25 through anaudio frequency transformer 26 and the left hand contact of anelectromagnetic switch 27, an electric space discharge amplifier tube-28fed from tube 25 through an audio frequency transformer 29, and aloudspeaking telephone receiver 30 fed from tube 28 through atransformer 31, the right hand contact of an electromagnetic switch 32and an adjustable volume control or voltage changing device 33. Asindicated by conductors 34, other volume control devices and loudspeakers may be connected to the output side of transformer 31 andlocated at any desired places.

A battery 40 supplies filament heating current for tubes 24 and 25through the left hand inner contact of a relay 42, left hand contact ofrelay 32, filament of tube 25, filament of tube 24, and a resistance 45.Steady potential for the gridv of tube 25 is supplied by the voltagedrop in the filament of tube 24 and in resistance .45.

An alternating current source 46 supplies current to the primary windingof a transformer 47. Current is also supplied from source 46 to theprimary windings of transformer 48 and transformer 49 through the righthand outer contact of relay 42. The secondary winding of the transformer47 supplies current for operating relays 7, 8, 42 and 32 through keys 9,10, 11 and 12.

A secondary winding 50 of transformer 48 has its mid-point grounded andsupplies alternating current for heating the filament of tube 28.

Alternating current from a secondary winding 51 of transformer 48 isrectified in a circuit extending from winding 51 through choke coil 52,resistances 55, 56 and 5'7 to earth, thence through conductor 60,resistance 65, conductor 66, the space discharge path of an electricspace discharge rectifier tube 6'7, to winding 51. A portion of winding51 supplies alternating current for heating the filament of rectifiertube 67. The voltage drop in resistance 65 is applied as steadypotential to the grid of tube 28, through a resistance 68 and thesecondary winding of transformer 29.

The voltage drop across resistance 57 is applied as steady potential tothe plate of tube 24, through the primary winding of transformer 26.

The voltage drop across resistances 56 and 57 is applied as steadyvoltage between the plate and the filament circuit of tube 25, vthroughthe primary winding of transformer 29.

The voltage drop across resistances 55, 56 and 57 is applied as steadyvoltage between the plate and the filament circuit of tube 28, throughthe primary winding of transformer 31.

The choke coil 52 and the condenser '70 reduce voltage fluctuationsacross resistances 55, 56, 5'1 and 65. A condenser'71 further reducesvoltage fluctuations across resistances 55, 56 and 57. A condenser '72further reduces voltage fluctuations across resistances 56 and 5'7. Acondenser '73 further reduces voltage fluctuations across resistance 57.Resistance 68 and a condenser 74 further reduce voltage fluctuationsapplied from resistance 65 between the grid and the filamentof tube 28,without substantially reducing the steady voltage applied fromresistance 65 to that grid. Condensers '71, '72 and 73 also providepaths of low impedance to signaling currents in the plate circuits oftubes 28, 25 and 24 respectively. As indicated by the broken linesrepresenting conductors leading from the set of keys 9, 10, ii and 12,this set of keys may, if desired, be remote from the condensers 15, 16,17, 15, 16', and 17', the connection of which to the receiver circuitthey control. For example, this set of keys may be located with a loudspeaking telephone receiver (not shown) connected to the conductors 34at a distance from the condensers, the tubes 24, 25 and 28 and the loudspeaker 30. As indicated by conductors '15, other sets of keys (notshown) like the set constituted by keys 9, 1'0, 11 and 12 may beemployed, the keys 9, 10, 11 and 12 being connected in multiple with thecorresponding keys, respectively, of each of such other sets. Such othersets may be located at any desired places. For example, one set may benear the tuning condensers and the loud speaker 30.

Pilot lamps such as '76 are connected to the 46 is supplying E. M. F. tothe transformer 48.

The armature of each of the relays '7, 8 and 42, in the absence ofcurrent in the windings of the relay, is held in the position to whichit was last operated by one of its windings. A holding spring is shownfor each of these relays, as representing means for thus holding thearmature. The winding of relay 32 is continuously connected in serieswith the secondary winding of transformer 4'7. Relay 32 is thereforemomentarily operated whenever one of the keys 9 to 12 is momentarilyoperated or, in other words, whenever either of the windings of relay'7, 8 or 42 is energized. In opening, relay 32 quickly opens its righthand contact, to disconnect from the secondary winding of transformer 31the volume control devices and loud speakers steady state.

32 prevents the production of noise in the loud speakers due to theaction upon the input circuits of tubes 24 and 25 of stray fields fromthe windings of relays 7, 8 and 42 when those windings are switched inor out of circuit by keys 9 to 12. The relay opens the circuit of thesecondary winding of transformer 31 before the stray field has time tochange materially; and the cooling of the filaments of tubes 24 and 25due to the opening of the filament circuit at relay 32 renders the tubesinoperative until the stray field has again reached a substantially Eachof the coils 18, 19 and 20 is, independently of the others, variablycoupled to the coil 22.

To adjust the system so that it. substantially instantaneously be set toselectively-receive;

signals transmitted on waves of any of three different wave lengths, saysignals from three broadcasting stations J, K and L (notshown) fromwhich it will be desired to receive signals more often than from otherstations, key 9 is first closed momentarily. Thereu, on, the left handwinding of relay 7, the right hand winding of relay 42 and the windingof relay 32 are energized over a circuit extending from the secondarywinding of transformer 47 through the winding of relay 32, key 9, aresistance 79, left hand winding of relay 7, and right hand winding ofrelay 42. Relay 32 operates momentarily. Relay 7 operates, or remainsoperated, to the left, remaining in that position after key 9 isreleased. Relay 42 operates, or remains operated, to the right,remaining in that position after key 9 is released. With relay 42 sooperated, the filament circuit of tubes 24 and 25 and the circuit of theprimary windings of transformers 48 and 49 are closed at its contacts.With relays 7 and 42 so operated, the antenna circuit extends fromantenna and coil 6 through the outer left hand contact of relay 7condenser 15 and coil 18 to ground; and the inner right hand contact ofrelay 7 connects condenser 15 across coil 22. Condensers 16, 17, 16' and17' and coils 19 and 20 are thus out of circuit. Now by adjustingcondensers 15 and 15' the system can be tuned to the wave length of,say, station J. Also, the coupling between coils 18 and 22 may beproperly adjusted for the intensity of the waves received by antenna 5from station J. The system is then conditioned for receiving signalsfrom station J, and thereafter if the operator has changed it to acondition for receiving signals of other wave lengths or to a conditionin which it is not responsive to signals of any wave length, it cansubstantially instantaneously be conditioned for receiving signals fromstation J by merely depressing key 9 momentarily.

The system having been adjusted so that it can substantiallyinstantaneously be set to selectively receive from station J, it maynext be adjusted so that it can similarly be set to receive from stationK. To so adjust it, key is first closed momentarily. Thereupon a circuitis m0- mentarily established extending from the secondary winding oftransformer 47 through the winding of relay 32, key 10, the left handwinding of relay 8, the right hand winding of relay 7, and the righthand winding of relay 42. Consequently, relay 32 operates momentarily,and relays 7, 8 and 42 operate or remain operated to the right, the leftand the right, respectively, remaining in those positions after key 10is released. With the relay 42 so operated to the right, the, filamentcircuit of tubes 24 and 25 and the circuit of the primary windings oftransformers 48 and 49 are closed at its contacts. With relays 7 and 8so operated, the antenna circuit extends from antenna 5 and coil 6through the inner left hand contact of relay 7, the outer left handcontact of relay 8, condenser 16 and coil 19 toground; and condenser 16'is connected across coil 22 through the inner right hand contact ofrelay 8 and the outer right hand contact of relay 7. Condensers 15, 17,and 17' and coils 18 and are then out of circuit. Now by adjustingcondensers 16 and 16' the system can be tuned to the wave length ofstation K. Also, the coupling between coils l9 and 22 can be properlyadjusted for the intensity of the waves received by antenna 5 fromstation K. The system is then adjusted for receiving signals fromstation K, and thereafter, if the operator has changed it to a conditionfor receiving signals of other wave length or to a condition in which itis not responsive to signals of any wave. length, it may besubstantially instantaneously conditioned for receiving signals fromstation K by merely depressing key 10, momentarily.

The system having been adjusted so that it can substantiallyinstantaneously be set to selectively receive signals from station J orstation K, it may next be adjusted so that it may similarly be set toreceive from station L. To so adjust it, key 11 is first closedmomentarily.

Thereupon a circuit is momentarily established, extending from thesecondary winding of transformer 47 through the winding of relay 32, key11, right hand winding of relay 8, right hand winding of relay 7, andright hand winding of relay 42. Consequently, relay 32 operatesmomentarily and each of relays '7, 8 and 42 operates, or

"remains operated, to the right, remaining so operated after key 11 isreleased. With the relay 42 so operated, the filament circuit of tubes24 and '25 and the circuit of the primary windings of transformers 48and 49 are closed at its contacts. With relays 7 and 8 so operated, theantenna circuit extends from antenna 5 and coil 6 through inner lefthand contacts of relays 7 and 8, condenser 17 and coil 20, to ground;and condenser 17 is connected across coil 22 through the outer right'hand contacts of relays 7 and 8. Condensers 15, 16, 15' and 16' andcoils 18 and 19 are then out of circuit. Now by adjusting condensers 17and 17 the system can be tuned to the wave length of station L. Also,the coupling between coils 20 and 22 can be properly adjusted for theintensity of the waves received from station L. The system is thenadjusted for receiving signals from station L, and thereafter if theoperator has changed it to a condition for receiving signals ofotherwave length, or to a condition in which it is not responsive to signalsof, any wave length, it may substantially instantaneously be conditionedfor receiving signals from station L by merely depressing key 11momentarily.

At any time, the system may be rendered unresponsive to signals of anywave length by depressing key 12 momentarily, whereby there isestablished momentarily a circuit extending from the secondary windingof transformer 47 through relay 32, key 12, a resistance 80, and lefthand winding of relay 42. Upon establishing this circuit, relay 32operates momentarily, and relay 42 operates to the left to break thefilament circuit of tubes 24 and and the circuit of the primary windingsof transformers 48 and 49.

Thereafter, as indicated above, key 9, 10 or 11 may be'operated wheneverit is desired to tune the system, substantially instantaneously to thewave length of station J, K or L, respectively.

Resistances 79 and 80 enable each of the windings of relays 7, 8, 42 and32 to have the same constants and yet receive the same value ofoperating current from transformer 47, resistance 79 having an absoluteimpedance substantially equal to that of one of said windings, andresistance 80 having an impedance twice the value of that of resistance79.

The condensers 15, 16, 1'7, 15, 16 and 17 may be of any suitable type,as for instance, rotary plate, air dielectric condensers of ordinarytype, and one pair of these condensers may be varied or adjusted to tunethe receiver to any desiredwithdrawn from circuit.

If desired, the constants of the antenna circuit or of the. circuit fedthereby may be maintained fixed, the tuning of the receiver beingaccomplished by varying only one of these circuits.

A phonograph 85 has a reproducer 86 and has start-stop mechanismrepresented, by way of example, by a brake 87. The start-stop mechanismwhen in position to prevent motion of the phonograph turntable opens aswitch 89 to maintain relay 27 deenergized. The grid or input circuit oftube is then closed through transformer 26, at the left hand contact ofrelay 2'7, in order that the radio receiver may be operated to reproduceradio signals received by antenna 5. When the start-stop mechanism is inposition to allow the phonograph to operate, switch 89 is closed, and,provided relay 42 is closed to the right, relay 27 will be energizedover a circuit extending from battery through left hand contacts ofrelays 42 and 32, winding of relay 27, and switch 89 to battery 40. Thisenergization of relay 2'? disconnects the transformer 26 from the gridof tube 25, so that the radio receiver will not operate to reproduceradio signals received by antenna 5 during the time that the phonographis operating. However, the radio receiver will automatically be renderedoperative to reproduce the radio signals when the phonograph is stoppedby the brake 8'7. The reproducer 86 is of the electrical type and is'connected to the primary winding of a transformer 90, the secondarywinding of which is adapted to be connected between the grid and thefilament of tube 25 by a front contact on relay 27. Thus, when thephonograph is operating, its electrical output from reproduc'er 86 isamplified by tubes 25 and 28 and converted into sound by the loudspeakers such as 30.

Obviously, if desired, an acousticphonograph may be employed and thebreak operated switch 89 used only to control the radio receiver inresponse to the starting or stopping of the phonograph.

Referring now to Fig. 2, an antenna circuit is shown, comprising anantenna 105, a variable inductance 107 and a variable condenser 100 connected to ground. A plurality of variable condensers such as 110, 111,112 and 113 are arranged to be optionally connected in shunt relation tocondenser 110 by the operation of looking keys, such as 120, 121, 122,and 123. Each of the keys upon being operated, is locked in closedposition by a locking bar or'member 129 which is urged to its lockingposition by a spring 131. Also, each of the keys, upon operation,releases the key last operated, the released key thereupon beingreturned to its open position by a spring such as 132.

The coil 107 is magnetically coupled to a coil 140, which forms part ofa tuned input circuit for an electric space discharge tube 145 which maybe a detector having its grid maintained at the proper biasing potentialby the usual blocking condenser 146 and leak resistance 147. The outputcircuit of the tube includes an indicating device, as for example, atelephone receiver 150. The tuned input circuit of the tube includes avariable condenser 100 shunted across coil 140, and adapted to have aplurality of variable condensers such as 110', 111', 112" and 113'optionally connected in shunt relation thereto by the keys 120 to 123.Condensers 100, 100', 110, 111, 112, 113, 110', 111, 112' and'113' maybe, 100 for example rotary plate, air dielectric condensers of ordinarytype.

To adjust this system so that it may substantially instantaneously beset to selectively receive signals transmitted on waves of any one offour different wave lengths, say signals from four broadcastingstations, J, K, L and M (not shown) from which it will be desired toreceive-signals more often than from other stations, key-120 is firstdepressed, releasing all of the keys 121 to 110 123. When keys 120 to123 have thus been operated, condensers 111 to 113 and 111' to 113' areout of circuit, and condensers 110 and 110' are in parallel relation tocondensers 100 and 100',

respectively. The circuit for condenser extends from the lower plate ofcondenser 100, through inner right hand contacts of keys 123, 122 and121 in series, and condenser 110, to ground. The circuit for condenser110' extends from the upper plate of condenser 100', through inner lefthand contacts of keys 123, 122, and 121 in series, and condenser 110, toground. With condensers 100 and 100' in any desired setting, condensers110 and 110' may now be adjusted to tune the system to, say, theshortest of the wave lengths of the four stations, asfor example thevwave length of station J. Thereafter, whenever the operator has changedthe station to a con dition for receiving signals of other wave lengthby operation of any of the keys 121, 122 or 123 as about to bedescribed, it can substantially instantaneously be conditioned or setfor receiving signals from station J by merely depressing key 120,provided the setting of condensers 100 and 100' has not been changed. 1The system having been adjusted -so that it can substantiallyinstantaneously be set for receiving from station J, it may next beadjusted so that it can substantially instantaneously be set to receivefrom station K. To so adjust'it, key 121 is depressed. Thereby condenser111 is connected in parallel relation to condenser 100 through a circuitextending from the lower plate of condenser 100, through the inner righthand contacts of keys 123 and 122, the outer right hand contact of key121, and condenser 111, to ground At the same time, condenser 111' isconnected in parallel relation to condenser 100', through a circuitextending from the upper plate of condenser 100' through inner left handcontacts of keys 5 123 and 122, outer left hand contact of key 121, andcondenser 111', to ground. Condensers 110, 112, 113, 110', 112' and 113'are now out of circuit, and, condensers 100 and 100' remaining in their6 former setting, condensers 111 and 111' may now be adJusted to tunethe system to receive from station K. Thereafter whenever the operatorhas changed the systemto a condition for receiving signals of other wavelength by operation of keys 122 or 123 as described below or byoperation of key 120 as described above, the system can substantiallyinstantaneously be conditioned for receiving signals from station K bymerely depressing key 121, provided the setting of condensers 100 and100' has not been changed.

The system having been adjusted so that it can substantiallyinstantaneously be set for selectively receiving from stations J and K,it may next be conditioned so that it can similarly be tuned to receivefrom station L. To so condition it, key 122 is depressed. Therebycondenser 112 is connected in parallel relation to condenser 100 througha circuit extending from the lower plate of condenser 100, through innerright hand contact of key 123, outer right hand contact of key 122, andcondenser 112, to ground. At the same time condenser 112' is connectedin parallel relation to condenser 100' througha circuit extending fromthe upper plate of condenser 100', through inner left hand contact ofkey 123, outer left hand contact 01 key 122, and condenser 112', toground. Condensers 110, 111, 113, 110', 111' and 113' are now out ofcircuit, and, condensers 100 and 100 remaining in their former setting,

condensers 112 and 112' may now be adjusted to tune the system toreceive from station L. Thereafter, whenever the operator has changedthe system to a condition for receiving signals of other wave length byoperation of key 123 as described below or by operation of key 120 or121 as described above, the system can substantially instantaneously beset for receiving signals from station L by merely depressing key 122,provided the setting of condensers 100 and 100' has not been changed.

The system having been adjusted so that it can substantiallyinstantaneously be set for selective- 1y receiving from stations J, Kand L, it may next be conditioned so that it can likewise be tuned toreceive from station M. To so condition it, key 123 is depressed.Thereby condenser 113 is connected in parallel relation to condenser 100through a circuit extending from the lower plate of condenser 100,through outer right hand conthrough outer left hand contact of key 123,and

condenser 113', to ground. Condensers 110, 111, 112,110', 111' and 112'are now out of circuit, and condensers 100 and 100' remaining in theirformer setting, condensers 113 and 113' may now be adjusted to tune thesystem to receive from station M. Thereafter whenever the operator haschangedthe system to a condition for receiving signals of other wavelength by operation of key 120, 121 or 122 as described above, thesystem can substantially instantaneously be set for receiving signalsfrom station M by merely depressing key 123, provided the setting'oicondensers 100 and 100 has not been changed.

Condensers 100 and 100' may be varied to thereby tune the system in theordinary way to any number of frequencies; but they must again be giventhe settings which they had while the system was being adjusted so thatcertain stations could be selected by depressing keys 120 to 123, whenit is desired to select those stations in that manner. Q

If desired, condensers 100 and 100' may be omitted from the system ofFig. 2, the capacity settings of the condensers controlled by keys 120to 123 then being made such that the capacities of those condensersserve as the total capacities for tuning the system to receive thesignals for which the keys are to condition the system. Whether or notthe condensers 100 and 100' are omitted from the circuit or adjusted'totheir zero capacity settings, one pair of the condensers 110 to 11-3 and110' to 113 may be varied or adjusted to tune the receiver to anydesired one of a range of wave lengths, including the'wave lengths ofthe stations to which the receiver is instantaneously tuned by the otherpairs. This variation of the capacities of the one pair will not disturbthe adjustment of the receiver for the instantaneous tuning by the otherpairs, since the operation of a key for causing any of the other pairsto be connected in circuit causes the one pair to be withdrawn fromcircuit.

If desired, the constants of the antenna circuit or of the circuit fedthereby may be maintained fixed, the tuning of the receiver beingaccomplished by varying only one of these circuits.

Referring now to Fig. 3, an antenna circuit is shown comprising anantenna 305 connected to ground through a tuning inductance 306, tuningcondensers 307 adapted to be optionally, or alter-. natively connectedin the circuit, and an inductance coil 308. The latter coil is variablymagnetically coupled to a tuning and coupling coil 310 which forms partof a tuned input circuit for an electric space discharge tube 315 whichmay be a detector having its grid maintained at the proper biasingpotential by the usual blocking condenser 316 and leak resistance 317.The output circuit of the tube includes an indicatin device, for examplea telephone receiver 320. The tuned input circuit of the tube includescondensers 325' adapted to be optionally connected in shunt relation toportions of coil 310 by a contact finger 325 movable over a bank ofcontacts of a rotary selector switch 326 such as is commonly employed inmachine switching telephone circuits. This selector switch alsocomprises contact fingers 330, 335, 340 and 345 and their banks ofcontacts, a stepping magnet 350 for driving the common shaft of all ofthe contact fingers, and a dialing device or circuit interrupting switch355 for interrupting the circuit through a battery 360, winding ofmagnet 350 and device 355 in order to automatically generate impulsescorresponding in number to. any numeral dialed for operating the magnet.Whenever the contact finger 345 is off of its normal or extreme lefthand contact, it may be returned to the normal contact by operating key365 to close a circuit extending from ground through battery 360, wind-I 140 densers 307 optionally in the antenna circuit. The finger 330 isadapted to vary the portion of inductance coil 306 included in theantenna circuit, and the finger 340 is adapted to vary the portion ofinductance coil 310 included in the tuned input circuit of tube 315.Thus the fingers 325, 330, 335 and 340 all cooperate in selecting thetuning reactances for tuning the system to selectively receivewaves ofdesired frequency.

The condensers 307 and 325' may be adjusted to tune the system to adifferent selected frequency for each position of the selector switch,and thereafter, the system can be tuned for receiving any desired one ofthese frequencies, when not already tuned to the desired one, by closingkey 365 long enough to permit the selector switch to step to its normalposition and then dialing a numeral corresponding to the number of stepswhich the selector switch must take to move from its normal position tothe position in which it will select the requisite reactances for thedesired tuning.

What is claimed is:

1. A circuit capable of operating at any frequency in a range offrequencies comprising means for substantially instantaneously renderingsaid circuit selective at will to waves of any desired one of aplurality of predetermined frequencies within said range, and means forrendering said circuit selective at will to waves of any desiredfrequency within said range of frequencies.

2. A circuit comprising means for substantially instantaneouslyrendering said circuit selective to waves of any desired one of aplurality of predetermined frequencies, and means for rendering saidcircuit optionally selective to waves of any desired frequency ina rangeof frequencies including a substantial portion of the frequency rangebetween the lowest and the highest of said predetermined frequencies.

3. A circuit comprising means for substantially v instantaneouslyrendering said circuit selective at will to waves of any desired one ofa plurality of predetermined frequencies, and means for rendering saidcircuit selective at will to waves of any desired frequency in a rangeof frequencies, including at least two of said predeterminedfrequencies, and means for varying the value of one of saidpredetermined frequencies cult to selectively receive any desiredfrequency of agiven frequency range, an additional holding key andcircuit connections whereby operation of said additional key causes saidvariable reactance to be rendered effective in tuning said circuit, andmeans responsive to the operation of any one of said holding keys tocause restora- 'tion of the one already operated, whereby the circuitmay instantaneously be tuned to any one of said plurality of frequenciesby the operation of the respective one of the first mentioned holdingkeys or be conditioned for variable tuning by the operation of saidadditional holding key.

5. A signal receiving circuit comprising tuning capacities, eachadjustable in value, for use in tuning said circuit to selectivelyreceive waves of any one of a plurality of frequencies, capacityselecting locking keys and circuit connections whereby each key uponoperation renders a different part of said capacities effective intuning said circuit, a variable condenser for tuning said circuit toselectively receive any desired frequency of a given frequency range, anadditional locking key and circuit connections whereby said additionalkey, upon operation, renders said variable condenser eifective in tuningsaid circuit, and means eflfective upon the operation of any one of saidlocking keys to release the one already operated, whereby the circuitmay instantaneously be tuned to any one of said plurality of frequenciesby the operation of the respective one of the first mentioned lockingkeys or be conditioned for variable tuning by the operation of saidadditional locking key. I

6. A signal receiving circuit comprising tuning reactances for use intuning said circuit to selectively receive waves of any of a pluralityof to be rendered effective in tuning said circuit,

a variable reactance for tuning said circuit .7

selectively receive any desired frequency of a given frequency rangeincluding a plurality of said predetermined frequencies, an additionalholding key and circuit connections whereby operation of said additionalkey causes said variable reactance to be rendered effective in tuningsaid circuit, and means responsive to the operation of any of saidholding keys for restoring the one already operated, whereby the circuitmay instantaneously be tuned to any one of said plurality of frequenciesby the operation of the respective one of the first mentioned holdingkeys or be conditioned for variable tuning by the operation of saidadditional holding 7. In a carrier wave signal receiving system, anelectric discharge device, a circuit therefor having input terminals, aplurality of reactance means each having a terminal connected to one ofsaid input terminals, a plurality of switching means each having acontacting member and a plurality of contacts, connections from anotherof said input terminals to the contacting member of one of saidswitching means, connections from one contact of said one of saidswitching means to the contacting member'of another of said switchingmeans, connections from another terminal of each of said reactance meansto corresponding contacts of respective ones of said switching means,and means responsive to the operation of each switching means forholding said switching means operated until the operation of another ofsaid switching means.

8. In a carrier wave signal receiving system according to the precedingclaim, another reactance means having a terminal connected to said oneof said input terminals and another terminal connected to the contact ofthe second mentioned switching means corresponding to that contact ofthe first mentioned switching means connected to the contacting memberof said second mentioned switching means.

9. In a carrier wave signal receiving system, an incoming circuit, anelectric discharge device, an input circuit therefor having inputterminals, a plurality of reactance means each having a terminalconnected to said incoming circuit, a

second plurality oi. reactance means each having a terminal connected toone of said input terminals, a switching means, a contacting member forsaid switching means connected to said incoming circuit, a contactassociated with said contacting member connected to another terminal ofone of said first mentioned reactance means, a second switching meanshaving a con- 'tacting member connected to a second contact said secondcontacting member and connected to another terminal of one of saidsecond reactance means, a second contact associated with said secondcontacting member, a second contacting member for said second switchingmeans connected to said second contact associated with said secondcontacting member of said first switching means, a plurality of contactsassociated with said second contacting member of said second switchingmeans and connected to other terminals of other of said second reactancemeans, and means responsive to the operation of either of said switchingmeans for maintaining such switching means operated until otherswitching means is operated.

MAURICE B. LONG.

